Large electrocaloric effects in single-crystal ammonium sulphate

Abstract

Electrocaloric effects are typically studied near phase transitions in ceramic and polymer materials. Here we investigate electrocaloric effects in an inorganic salt, namely ammonium sulphate (NH$_4$)$_2$SO$_4$, with an order-disorder transition whose onset occurs at 223 K on cooling. For a single crystal thinned to 50 $\mu$m, we use a Maxwell relation to find a large isothermal entropy change of 30 J K$^{-1}$ kg$^{-1}$ in response to a field change of 400 kV cm$^{-1}$ . The Clausius-Clapeyron equation implies a corresponding adiabatic temperature change of 4.5 K.